Silent chain drive



July 28, 1931. R. w; DULL ET AL -S ILENTCHAIN DRIVE Filed Aug. 21. 1929 3 Sheets-Sheet l l @ma .July 28, 1931. '4 R. w. DULL ET AL 1,816,473

, SILENT CHAIN RIvE Filed Aug. 21. 1929 3 Sheets-Sheet 2 [72 venan? L b Erz@ Geer @mfG/orngyj July 28, 1931.

R. w. BULLET-AL;

SILENT CHAIN DRIVE Filed Aug. 21. 1929 5 Sheets-Sheet 5 y chain tooth and 'one side of the sprocketA toot vPatented July 28, 1931 RAYMOND W. I ,ULL,OIv CHICAGO, ILLINOIS, AND ERIC. GEnR'rz, or INDIANAPOLIS,

A INDIANA, A

POI'tATION OF ILLINOIS ssIGNoRs To LINKTBELT COMPANY, or CHICAGO, ILLINOIS, A COR- fsILENr CHAIN DRIVE'- Application mea August 21, 1929; serial No. 387,537.

.drive chain, a, so-called stub sprocket tooth', the length of the tooth being such that when lthe chain is pushed home so that it, engages the root circle of the tooth there is still always clearance between 'the end of the tooth and the chain, andthe lrelation between the thickness of the tooth and the distance be-r tween the chain teeth is such that only one canbeincontact at lthe same' time.

#Among the objects of our invention are: to provide a chain sprocket drive which will be inexpensive to manufacture, silent, and` wherein ay substantially constant speed relation between'the chain and the sprocket will prevail. Another object of our invention is so fto relate the` chain faces ofthe sprocket teeth and, chain teeth that thechaiv'n willenterk and leave the sprocketsubstantially"along a tangent to the pitchcircle, thereby lsubstan-` tiallyv avoiding vlongitudinal and transverse vibrationof thechain'. Another 'object is to provide a chain and/chain sprocket so re; latedthat'there never can `be anything except single point contact between the sprocket toot-hand anyone of the chain links, so that the sprocket tooth may never be wedged into the pocket betweenthe two adjacent' teeth on a single chain link, thus preventing harshness and vibrationjwhich would'result from such -wedging if that lwere possible.

By working surfaces we-mean "those sur# faces on the chain tooth and on the sprocket tooth which ycome together to establish a driving relation between chain and sprocket. By inside Contactv we mean va Achain and sprocket relationwherein the working sur-4 faces on the chain are not at the ends of the link but form' the sides of the gap or pocket between the-two teeth on the link, and wherein, therefore, the working surfaces on any chain link arelocated, not beyond the pivot. points of the link, but between the link pivot points;

Our preferred form of link is, then, an inside'contact link wherein the relation between the width of the gap between the two link working surfaces and the sprocket tooth with which they co-operate, and the length of the .tooth above vthe rootlcircle,'vis such that contact between the chain and sprocket can occur yonly between the non-working ends of side of the sprocket 'tooth and one, and only one, of the two teeth on each chain link.

Our invention is illustrated more or with pintles in section;

less diagrammatically in thev accompanying, 3

Figure 3 isa similar view of the lower half of the sprocket IPlfrlzjra'rf OFFICE ooi . the teeth and the rootv circle and between one- Figure l is a plan view of a portion of the chain.

A is a driving gear or sprocket having teeth A 1. A2" is the driven gear or sprocket having teeth A3.- rIraveling about these two sprockets is asilent chain made up of a. series of separate link members A5, each having two chain teeth A6 A7 one at each end of the link.

The' interior opposed .surfaces'of these teeth: are the working surfaces, the outer surfaces are cut away so that, no matter what the position of the chain, they lie inside the con-y tour of the interior working surfaces, and the interior working surfaces onlyv are able to engage the sprocket teeth. These chain links cio:

are assembled into a chain beltby means of i pivot pins A8 upset at YA9 against holding washers A1". We have shown forpurposes of illustration only these pins as being solid; theymight be built up, they might be hollow,

theirparticular shaper and arrangement is ofv v no consequence in so far as our present invention is concerned, it being merelyy neces 10@ sary that they join the separate chain links together in interlocking overlapping relation so as to provide a continuous chain belt which travels about the sprockets with the chain teeth engaging the sprocket tooth. The teeth on a plurality of links are in line t0. form, in effect, a series of composite teeth which engage a series of sprocket teeth in driving relation. y

The relation between the chain teeth As A7 and the sprocket tooth A1 or A3 which enters between them is such that there is never a simultaneous contact between the sprocket tooth and the tivo chain teeth between which it enters, but only contact between one side of the sprocket tooth and one of the interior working surfaces `on the link, that is, there is never a simultaneous contact between a sprocket tooth and they working surfaces of two chain teeth on the saine link. This insured because, owing to the shortness of the Stub tooth when the end point of either one or bothof the chain teeth engages the cylindrical root circle adjoining the teeth on the sprocket, the chain link is held away far enough so that there must always be clearance between one side of the sprocket tooth and one of the` teeth onany individual link when there is engagement between the other side of the same sprocket tooth andthe other tooth on such firstnnentioned link. Of course, the position may be such that there is clearance on both sides, but there never is simultaneous contact.

Referring now to Figure l, the sprocket tooth which we have numbered l has just engaged the chain tooth 1 and there is a wide clearance B between the following tooth of that same link and the sprocket tooth. The sprocket tooth 2 has engaged the". leading chain tooth 2 and there is a narrower' clearance B1 betweenthe back of the sprocket tooth and the following tooth of thelink. This narrower clearance B1 persists as travel takes place around the sprocket with the sprocket tooth engaging the working surface on the back of the leading tooth of'each chainlink until some intermediate or transition point is reached asat 3, where there is a clearance B2 between the sprocket tooth and both of the working; furthe chain teeth. This clearance is found also in connection with the neXt tooth 4, Then tooth No. 5, however, is reached, the position of the clearance B4 has moved and we now find that the sprocket tooth is in engagement with the working faces on the following chain tooth instead of the leading chain tooth, and this continues until the position 6 is reached, at which point the sprocket tooth is finally entirely out of contact with the chain and the chain is free to move away from the driving sprocket on its Way to the driven sprocket, this side'of the chain being the slack side as distinguished from the upper or incoming side, which is the tight side.

leading side of the sprocket tooth andthe working surfaces ofthe leadingfchain link prevails back as farl as the transition point 1l, where there is clearance C1 on both sides of the sprocket tooth and no cont-act between it and either of the chain teeth. Beyond this point, Vfor instance at 12, the relation is reversed and the contact is between the sprocket tooth and the leading chain tooth with clearance at C?. This condition prevails throughout the remainder'of the area of 'contactbe4 tween the chain and sprocket.

Itinay even occur that there will be no such floating link, because it is possible that the transition will take place and be co1npleted within'a distance of less than one pitch. tionbetweenvthe chain and the sprocket, the speed, the load, and :the chain'tension, the angularposition of the. transition point varies through a fairly wide range within the total angle of contact between sprocket and chain. l

Referring now to Figures 2 and 3, there is illustrated on a larger scale the relation between the sprocket and the chain as the chain winds about the driver.` It will be notedthat in'the initi-al'position toward the right there is contact 'between the' working face of the `cha'intooth toward its point and the forward working face'of the sprocket tooth toward-'its base. As these two teeth r'oll and slide together as indicated diagralnmatically in Figure 2, the line of contact moves outardlyjfrom'the center of rotation of the' sprocketwuntil on the eXtreme left of Figure 2 the driving sprocket tooth toward its pointgengages the chain tooth toward its base'. Tn Figure 3 the same thing is shown as applied tothe leaving side of the driving sprocket. Here the slack chain as it leaves the sprocket is held back by the sprocket, and so there is a contact'between'the following side of the sprocket tooth andv the' following chain link tooth, as contrasted-with the-con'- tact betweenthe' le'adingside'of the 'sprocket tooth and the leading chaintooth in Figure 2. The same slidingan'd rollingaction occurs so that the vcontact between the chain and sprocket" teeth travels inwardly as the chain leaves the sprocket from the'le'ft hand position with contact between the top of the sprocket too'th and the'base of the chain tooth to contact between the ti-p of the 'chain teeth andthe base ofthe sprocket tooth, the dis-V placement' of this line of contact being along the ldot and dashline 'as indicated.'

Also depending upon the pitchfrelal.

The same `relation prevails both with the driving and with the driven sprocket chain. If we regard the sprocket as being driven, then the chain of Figure 3, instead of being the slack side, will be the tight side and the chain of Figure 2, instead of being the tight side, will be the slack side of the chain, but f the relation between the teeth on sprocket and c chain would be the same in each case.

In Figures 2 and 3 is shown the position which may be assumed by the chain on the sprocket, for instance as the result of wear. The total length of the chain under these conditions will increase as shown. The result is that the links ride out along the sprocket tooth in the well known manner, but no matter how great this wear the relation remains the same, in so far as the fact is concerned y that no individual chain link can ever touch both sides of the sprocket tooth with which it is related, because its inward movement tending to wedge it on that tooth is limited yso before such wedging action takes place, by engagement between the two ends of such link tooth and the root circle of the sprocket.

vIn Figure l the chain is shown as having root Contact with the sprocket throughout the entire arc of contact with the sprocket. This is, ofcourse, not the condition prevail ing when the chain is running but may prevail while the chain is Vat rest. The drawing was made this way to point out and emphasize the fact that'in our chain sprocket combination, even when the chain is forced as far inv as it can go resulting rin root Contact, still there can never be simultaneous contact between a sprocket tooth and both of the teeth of the link straddling it. That is, our combination permits single interior contact but never under any circumstances double interior contact.

In actual running our chain may approach the position of root contact at the transition point where the tension on theV chain parts ispractically nil and everywhere else the chain distinctly tends to ride radially away from the position of root contact.

We claim:

l. In combination, a toothed sprocket and` a chain comprising a plurality of inside contact toothed chain links, all of the links forming the chain being identical, and means for positively preventing engagement of any sprocket tooth with more rthan one of the teeth on each link at one time, said means comprising the face `of the sprocket between adjacent sprocket teeth.

2. In combination with a toothed sprocket and chain comprising a plurality of inside contact toothed chain links, all of the linksv forming the chain being identical, there being a tapered pocket formedbetween two teeth on each link of such width that when the ends of the teeth rest on the sprocket on opposed sides of the tooth which penetrates the pocket, the tooth can engage one sidev of the pocket only at one time.'

3. In combination with a toothed sprocket, a chaincomprising a plurality of inside contact toothed chain links, all of the links forming the chain being identical, there being a tapered pocket formed between two teeth in each link of such width that when the ends of the teethv rest on the root surface of ing the chain being identical, a pocket formed between two teeth in each link, the sprocket tooth being shorter than the link teeth with which it cooperates measured along radial lines yabout the center of the sprocket.

Signed at Chicago, county of Cook andA State of Illinois, thisvlth day of August, 1929. f

RAYMOND `W. DULL.

Signed at Indianapolis, in the county of Marion, and State of Indiana, this 16th day of August, 1929. l

ERIC GEERTZ. l 

